The purpose of this proposal is to develop a registry for the collection of epidemiological data on Alzheimer's disease and other dementias and to provide training facilities for personnel in the collection of such data. The Rochester (Minnesota) Epidemiologic Program Project (REPP) is a unique population-based data resource which can provide rates and clarify risk factors and outcome for Alzheimer's disease. This resource is comprised of the medical records of all persons residing in Olmsted County, Minnesota. A pilot study has demonstrated that this data bank will serve in a superb fashion as a registry and training facility for epidemiologic data concerning the incidence, trend, prevalence and outcome of Alzheimer's disease and other specific forms of dementia in this population. It is proposed that such data be obtained for the period 1960 through 1984 and it is expected that about 1,050 cases of dementia, including nearly 650 cases of Alzheimer's disease, will be identified for the 182,000 person-years represented in the elderly population of the county over that time span. In addition to the above-mentioned descriptive epidemiological studies based on case records review, we propose to conduct two types of analytical epidemiologic studies: first, research into risk factors for dementing illnesses, using an efficient and representative method of control selection from the entire medical record data bank for this population; and second, a limited prospective study of Olmsted County residents which will address logistic issues and emphasize the development and testing of screening procedures and an assessment of test procedures and suspected risk factors. There is also the opportunity of comparing the demographic and clinical features of Alzheimer's disease in the County population (total case ascertainment) with the cases in the large Mayo Clinic referral practice, which should help identify patient selection bias and the extent of distortion associated with the use of case series in referral centers. This proposal also addresses the question of the merits of local and "national" registries, various methods of data collection, and the advantages and disadvantages of each method.